ARCHIVED REPORTS XR0006987 - Laserfiche WebLink

Home Browse Search

' In thL sits snlisuitaLL (that \Mould ser',L to Dalt verl]Laf migration of the contaminants) theictore was not ahsLilcd rloi indicated Althuuglr i Li}mining unit (laterally and vertically evtLnsivL with high clay Lontent) was not obscired at the site, ' virtually ,ill Of thL subsurtaLL is Lonhposcd of a iclativciy tight fine-grained matrix that should sLiyL to Inhibit the vertical migration of Lontanhinants I he laboratory analytical results of the soil and groundwater samples ' indicated that only traLL' LonLerltrations of M IBI were present In } roundwater from the deeper SMI strata at the IoLations IIivLstlaatLd ' ]hL rLsults of the Soil and gioundwatLr II1vc.stlgat]on Indicated that the MTBE plume generally extends in relatively low concentrations in shallow groundwater beyond the drainage ditch and into the agricultural field to llle Cast cit tl1C sitL ItLlAACly high MT131- LonLentrations are present in shallow groundwater to the west of the drainage ditch south Last of site I1l0nitor well MV4 The Loncentration of MTBF present at the location of DP- ' 5 rS appromniately thILL orders of magnitude greatLI than thL LonLentratlon of MTBE at the IoLatlon of DP-9 i his relatively lapid attenuation of M 1 131 Loncentrations suggests that the MTBE; plume is being truncated by ' the ]hydraulic Influence exerted by the island drainage channel pumping that oLLurs at the south portion of the site I hL sLrisitive it ceptor survey did not Indicate any readily identifiable sensitive receptors within a radius of 2,000-feet around the site (other than the surface water bodies adjacent to the site) Based on the results of the soil and groundwater investigation, Condor recommended that an engineered approach to iemediation of the MTBE; plume not be initiated Alternatively, Condor recommended further investigation and monitoring of the apparent leading edge of the MTBE plume rather than conducting remedial ' operations bLyond what is presently occurring at the site Additional extraction and treatment of W BE at the site would bL a NLiy LxpLnsivc and time-consuming approach with a low chance of technical success or results Condor spLLifiLa]ly rLLomiriended continuing the current quarterly surface and groundwater monitoring program at thL sltL C ondor also rLLommended additional groundwater Investigation in the area south, southeast, and southwest of MW-2, along Eight Mile (toad, to verify containment of the south extent of the MTBF plumL by the ' island drainage channel pumping In addition the installation development, surveying and sampling of additional monitor wells was recommended to be conducted in a subsequent phase to verify the results of the past and proposed soil and groundwater investigation and to monitor the extent of the MTBE plume The additional ' monitor wells would include at least one monitor well located at the anticipated cast lateral extent of the MTBE plume which would be screened in the deeper strata ' In addition ( onclor further recommended that the groundwater sampling of site monitor well MW-1 be dISLOIItiililLd of ILdIILLd to an annual frequency This iccommendation is based on the results of several successive quaiteily monitoring events that indicate that petroleum hydrocaibons are not present at or above the ' laboratory reported detection limits at that location 1 1